Springboot整合AOP和注解，实现丰富的切面功能

简介

我们在文章《Spring AOP与AspectJ的对比及应用》介绍了AOP的使用，这篇文章讲解一下AOP与注解的整合，通过注解来使用AOP，会非常方便。为了简便，我们还是来实现一个计时的功能。
整合过程

首先创建一个注解：

1. @Retention(RetentionPolicy.RUNTIME)
2. @Target(ElementType.METHOD)
3. public @interface PkslowLogTime {
4. }

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然后在一个Service中使用注解：

1. @Service
2. @Slf4j
3. public class TestService {
4.     @PkslowLogTime
5.     public void fetchData() {
6.         log.info("fetchData");
7.         try {
8.             Thread.sleep(500);
9.         } catch (InterruptedException e) {
10.             throw new RuntimeException(e);
11.         }
12.     }
13. }

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这个Service的方法会在Controller中调用：

1. @GetMapping("/hello")
2. public String hello() {
3.   log.info("------hello() start---");
4.   test();
5.   staticTest();
6.   testService.fetchData();
7.   log.info("------hello() end---");
8.   return "Hello, pkslow.";
9. }

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接着是关键一步，我们要实现切面，来找到注解并实现对应功能：

1. @Aspect
2. @Component
3. @Slf4j
4. public class PkslowLogTimeAspect {
5.     @Around("@annotation(com.pkslow.springboot.aop.PkslowLogTime) && execution(* *(..))")
6.     public Object doAround(ProceedingJoinPoint joinPoint) throws Throwable {
7.         log.info("------PkslowLogTime doAround start------");
8.         MethodSignature methodSignature = (MethodSignature) joinPoint.getSignature();
10.         // Get intercepted method details
11.         String className = methodSignature.getDeclaringType().getSimpleName();
12.         String methodName = methodSignature.getName();
14.         // Measure method execution time
15.         StopWatch stopWatch = new StopWatch(className + "->" + methodName);
16.         stopWatch.start(methodName);
17.         Object result = joinPoint.proceed();
18.         stopWatch.stop();
19.         // Log method execution time
20.         log.info(stopWatch.prettyPrint());
21.         log.info("------PkslowLogTime doAround end------");
22.         return result;
23.     }
24. }

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@Around("@annotation(com.pkslow.springboot.aop.PkslowLogTime) && execution(* *(..))")这个表达式很关键，如果不对，将无法正确识别；还有可能出现多次调用的情况。多次调用的情况可以参考：Stackoverflow
这里使用了Spring的StopWatch来计时。
测试

通过maven build包：

1. $ mvn clean package

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日志可以看到有对应的织入信息：

1. [INFO] Join point 'method-execution(java.lang.String com.pkslow.springboot.controller.TestController.hello())' in Type 'com.pkslow.springboot.controller.TestController' (TestController.java:22) advised by around advice from 'com.pkslow.springboot.aop.ControllerAspect' (ControllerAspect.class(from ControllerAspect.java))
2. [INFO] Join point 'method-execution(java.lang.String com.pkslow.springboot.controller.TestController.hello())' in Type 'com.pkslow.springboot.controller.TestController' (TestController.java:22) advised by before advice from 'com.pkslow.springboot.aop.ControllerAspect' (ControllerAspect.class(from ControllerAspect.java))
3. [INFO] Join point 'method-execution(void com.pkslow.springboot.controller.TestController.test())' in Type 'com.pkslow.springboot.controller.TestController' (TestController.java:31) advised by around advice from 'com.pkslow.springboot.aop.ControllerAspect' (ControllerAspect.class(from ControllerAspect.java))
4. [INFO] Join point 'method-execution(void com.pkslow.springboot.controller.TestController.test())' in Type 'com.pkslow.springboot.controller.TestController' (TestController.java:31) advised by before advice from 'com.pkslow.springboot.aop.ControllerAspect' (ControllerAspect.class(from ControllerAspect.java))
5. [INFO] Join point 'method-execution(void com.pkslow.springboot.controller.TestController.staticTest())' in Type 'com.pkslow.springboot.controller.TestController' (TestController.java:37) advised by around advice from 'com.pkslow.springboot.aop.ControllerAspect' (ControllerAspect.class(from ControllerAspect.java))
6. [INFO] Join point 'method-execution(void com.pkslow.springboot.controller.TestController.staticTest())' in Type 'com.pkslow.springboot.controller.TestController' (TestController.java:37) advised by before advice from 'com.pkslow.springboot.aop.ControllerAspect' (ControllerAspect.class(from ControllerAspect.java))
7. [INFO] Join point 'method-execution(void com.pkslow.springboot.service.TestService.fetchData())' in Type 'com.pkslow.springboot.service.TestService' (TestService.java:12) advised by around advice from 'com.pkslow.springboot.aop.PkslowLogTimeAspect' (PkslowLogTimeAspect.class(from PkslowLogTimeAspect.java))

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启动应用后访问接口，日志如下：

总结

通过注解可以实现很多功能，也非常方便。而且注解还可以添加参数，组合使用更完美了。
代码请看GitHub: https://github.com/LarryDpk/pkslow-samples

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